烤烟叶丝微波干燥特性研究

分析了烤烟叶丝含水率和温度随微波作用时间的变化规律并绘制出叶丝微波干燥曲线,研究了不同工艺条件(微波功率、叶丝初始含水率、真空压力)对叶丝微波干燥曲线的影响,在此基础上,建立了烤烟叶丝微波干燥的数学模型。结果表明,烤烟叶丝的微波干燥大致分为3个阶段:第1阶段,干燥速率和温度上升迅速,含水率降低缓慢;第2阶段,干燥速率基本保持不变,温度上升缓慢,含水率下降迅速;第3阶段,干燥速率下降,温度上升缓慢,含水率下降缓慢。微波功率和叶丝初始含水率对叶丝微波干燥曲线的影响显著,而真空压力影响不显著。烤烟叶丝微波干燥的动力学过程可以用薄层干燥的数学模型Page方程描述。

Study on Cut Tobacco Drying by Microwave

The changes of moisture content and temperature of cut lamina of flue-cured tobacco versusmicrowave dryingtime were analyzed and the drying curve was drawn.The effects of various processingconditions,suchas microwave power,theinitial moisture content of cut lamina and vacuumpressure,onthe curve were studied,andthe mathematic model of microwave drying was established.It indicatedthatthe drying process could roughly be divided into three stages :duringthe first stage,the drying velocityandtemperature of cut laminaincreased promptly,while the moisture content reduced slowly;duringthesecond stage,the drying velocity kept constant andthe temperature increased slowly,while the moisturecontent decreased quickly;duringthe third stage,the drying velocity slowed down and moisture contentdecreased tardily,thetemperatureincreasedslowly.The higherthe power of microwave,the more rapidlythe moisture content decreased andthetemperatureincreased;the highertheinitial moisture content,themore rapidlythe moisture content decreased andthe lower the final temperature was;however,the effectof vacuumpressure was not significant.The dynamic process of cut tobaccoin microwave dryingcould bedescribed mathematically by Page equation of thinlayer drying.